Capcom knows it a risk but they also know there are successes when you can find the right formula. They found that for RE series of games but Dead Rising didn't work. And the RE games have been mostly remakes and not much investment and time needs to be put into them as say a new IP built from the ground up.
Let me state it again. The Wii, for better or worse, has a large family friendly audience. M rated games may sell to the core but unfortunately, there are more families that own a Wii then the lone core gamer. If I am a company trying to sell to the majority of the userbase, looking for that 5-10% attach rate, I have to look at the games that have done it in the past. That is why you are getting a RE-Wii remake, a Dead Space on Rail shooter, and probably a Wii Modern Warfare 2. But that is also why you are getting Punch Out, Wii Sports Resort, EA Active Fitness, and Beatles: Rock Band. Because they are going after the large part of the userbase.